Major Customers and Concentrations of Credit Risk - Sales to Major Customers (Details) - Customer Concentration Risk - Revenue from Contract with Customer Benchmark	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Boeing
Revenue, Major Customer [Line Items]
Concentration percentage	10.50%	16.60%	17.00%
Lockheed Martin
Revenue, Major Customer [Line Items]
Concentration percentage	5.00%	4.00%	4.40%
Northrop
Revenue, Major Customer [Line Items]
Concentration percentage	9.10%	4.00%	3.60%
Raytheon
Revenue, Major Customer [Line Items]
Concentration percentage	20.90%	15.60%	16.30%
Spirit
Revenue, Major Customer [Line Items]
Concentration percentage	3.30%	12.20%	9.50%
Top Ten Customers
Revenue, Major Customer [Line Items]
Concentration percentage	61.10%	65.40%	65.30%